text: /*
  * Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
  *
  * This software is provided 'as-is', without any express or implied
  * warranty.  In no event will the authors be held liable for any damages
  * arising from the use of this software.
  * Permission is granted to anyone to use this software for any purpose,
  * including commercial applications, and to alter it and redistribute it
  * freely, subject to the following restrictions:
  * 1. The origin of this software must not be misrepresented; you must not
  * claim that you wrote the original software. If you use this software
  * in a product, an acknowledgment in the product documentation would be
  * appreciated but is not required.
  * 2. Altered source versions must be plainly marked as such, and must not be
  * misrepresented as being the original software.
  * 3. This notice may not be removed or altered from any source distribution.
  */
  
  #ifndef B2_WELD_JOINT_H
  #define B2_WELD_JOINT_H
  
  #include "Box2D/Dynamics/Joints/b2Joint.h"
  
  /// Weld joint definition. You need to specify local anchor points
  /// where they are attached and the relative body angle. The position
  /// of the anchor points is important for computing the reaction torque.
  struct b2WeldJointDef : public b2JointDef
  {
  	b2WeldJointDef()
  	{
  		type = e_weldJoint;
  		localAnchorA.Set(0_fx, 0_fx);
  		localAnchorB.Set(0_fx, 0_fx);
  		referenceAngle = 0_fx;
  		frequencyHz = 0_fx;
  		dampingRatio = 0_fx;
  	}
  
  	/// Initialize the bodies, anchors, and reference angle using a world
  	/// anchor point.
  	void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
  
  	/// The local anchor point relative to bodyA's origin.
  	b2Vec2 localAnchorA;
  
  	/// The local anchor point relative to bodyB's origin.
  	b2Vec2 localAnchorB;
  
  	/// The bodyB angle minus bodyA angle in the reference state (radians).
  	float32 referenceAngle;
  	
  	/// The mass-spring-damper frequency in Hertz. Rotation only.
  	/// Disable softness with a value of 0.
  	float32 frequencyHz;
  
  	/// The damping ratio. 0 = no damping, 1 = critical damping.
  	float32 dampingRatio;
  };
  
  /// A weld joint essentially glues two bodies together. A weld joint may
  /// distort somewhat because the island constraint solver is approximate.
  class b2WeldJoint : public b2Joint
  {
  public:
  	b2Vec2 GetAnchorA() const override;
  	b2Vec2 GetAnchorB() const override;
  
  	b2Vec2 GetReactionForce(float32 inv_dt) const override;
  	float32 GetReactionTorque(float32 inv_dt) const override;
  
  	/// The local anchor point relative to bodyA's origin.
  	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
  
  	/// The local anchor point relative to bodyB's origin.
  	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
  
  	/// Get the reference angle.
  	float32 GetReferenceAngle() const { return m_referenceAngle; }
  
  	/// Set/get frequency in Hz.
  	void SetFrequency(float32 hz) { m_frequencyHz = hz; }
  	float32 GetFrequency() const { return m_frequencyHz; }
  
  	/// Set/get damping ratio.
  	void SetDampingRatio(float32 ratio) { m_dampingRatio = ratio; }
  	float32 GetDampingRatio() const { return m_dampingRatio; }
  
  	/// Dump to b2Log
  	void Dump() override;
  
  protected:
  
  	friend class b2Joint;
  
  	b2WeldJoint(const b2WeldJointDef* def);
  
  	void InitVelocityConstraints(const b2SolverData& data) override;
  	void SolveVelocityConstraints(const b2SolverData& data) override;
  	bool SolvePositionConstraints(const b2SolverData& data) override;
  
  	float32 m_frequencyHz;
  	float32 m_dampingRatio;
  	float32 m_bias;
  
  	// Solver shared
  	b2Vec2 m_localAnchorA;
  	b2Vec2 m_localAnchorB;
  	float32 m_referenceAngle;
  	float32 m_gamma;
  	b2Vec3 m_impulse;
  
  	// Solver temp
  	int32 m_indexA;
  	int32 m_indexB;
  	b2Vec2 m_rA;
  	b2Vec2 m_rB;
  	b2Vec2 m_localCenterA;
  	b2Vec2 m_localCenterB;
  	float32 m_invMassA;
  	float32 m_invMassB;
  	float32 m_invIA;
  	float32 m_invIB;
  	b2Mat33 m_mass;
  };
  
  #endif
  